1. Field of the Invention
This invention generally relates to mounts for movable machineries such as an reciprocating engine, and more particularly, to a combination viscous and resilient type of mount for damping or insulating vibrations.
2. Description of the Related Art
A wide variety of mounts have been proposed to resiliently support a moving machinery and prevent the vibration of the machinery being transmitted to another component.
European patent application No. 115,417 discloses a hydraulically damped mounting device where the damping is achieved at least partially by hydraulically. The disclosed mounting device typically includes two different anchor points joined by a resilient spring made of rubber. The resilient spring and a partition cooperate to form a working chamber for viscous fluid. The working chamber is communicated with a compensation chamber through a passage. The compensation chamber is bounded by a flexible bellow and is thus capable of expanding and contracting so as to compensate for the movement of the fluid between the two chambers. A flexible diaphragm is provided in a manner to directly contact the fluid in the working chamber and acts as a barrier between the fluid and a gas. Relative movement of the anchor points causes a change in pressure in the working chamber. High frequency vibrations are absorbed by movement of the diaphragm with little resistance, and low frequency vibrations cause fluid movement through the passage with a strong damping effect.
Upon application of a downward thrust to the resilient spring, it tends to be bent outwardly or expand due to its nature and shape. This tendency causes a reduction in the effective area of the piston or resilient spring. The reduction in the effective area of the spring results in a lesser damping effect.
There is another disadvantage to the prior art mounting device. Specifically, the resilient spring is subject to radiation heat or thermal effects by an engine and the like. The temperature of the fluid in the chambers will increase with increasing ambient temperature. Changes of the temperature in the fluid will affect the viscosity of the fluid and thus damping effects. The higher the temperature of the fluid, the weaker the damping effect.